How to replace C-max hybrid 12v battery

[djc]

I didn't see a post on this.  I did see a youtube video on the Energi, but it is slightly different, and he didn't run into a problem whereas I did.

 

My 12v battery was not holding charge since last sub-zero cold spell and only short trips to charge it.  Dead thrice in driveway. The state of the 12v battery charge can be checked under the hood.  Mine was regularly 11.6 volts after long charging.  Should be 12.6.  I believe it is the original battery.

 

New battery $135 at dealer.  core deposit $16 (varies by state, I believe).  Dealer had quoted $80 labor to install.

 

Tools: socket wrench.  10mm and 8mm sockets.  extension.  T25 torx screwdriver (I used a T25 bit in a portable drill).

  I also needed a vise-grips; not expected.  Also Liquid Wrench.   Pliers maybe useful.

 

Look under the car and check the 1 inch or so of screw sticking out of the bottom of the battery box (the end of the battery hold down).  It if is corroded, spray with penetrating oil.  Doing this first will give the penetrating oil some time to, well, penetrate.  More on this later.

 

Lift soft cover just inside hatch and prop up with something. 

Remove 3 T25 black screws along top edge of the big plastic liner that covers the battery and has the little white funnel in it.   

Remove 10mm nut just to the left of the positive terminal of the battery, the last thing holding the liner in. 

Pull back the top edge of the liner and at same time lift the rear edge.  It should pop up and out.

The left 2/3 of the space now visible has a fan and duct for the HVB.

 

Battery:  loosen (don't remove) the 10mm on the negative pole, lift terminal off and swing left.   On mine the terminal could be caught under the edge of the hatch carpet to hold in place.  Can wrap a cloth or plastic or sock or a plastic bag over the end if it doesn't want to stay out of the way.

Loosen the 10mm bolt on the positive terminal.  Since the negative is disconnected, won't arc, but doesn't hurt to be careful to avoid contacting wrench handle to metal.  Lift positive terminal assembly left and out of the way.

 

Last: remove the battery hold down.  This proved very difficult.  A long screw with an 8mm head sticks up from the plastic hold down.  Mine refused to turn, and then turned without unfastening.  Turns out it screws into a piece under the battery holder and so under the car. Have to go under the bumper to get to it, but it is not far in so easy reach.  I ended up using vise grips and liquid wrench, one hand holding the visegrips under the car, the other turning the wrench on the 8mm hold down screw inside the battery box.

 

Lift out the battery holddown (black T-shaped plastic with the long screw); pliers might help to pull up the plastic holddown.

Tip the pos end of the battery up and pull back part way.  Unfasten the rubber gas tube from the negative end of the battery (it is friction fit into a hole just below the top of the battery along the edge farthest away from you).  Then lift battery out at an angle.

 

On the Energi, he had to remove a metal crosspiece over the back of the battery; not necessary on C-max.

 

Replace - insert new battery part way and fasten out-gassing tube in new battery.  Slide battery rest of the way in.  Easiest to fasten neg terminal with battery not all the way back (so before reattaching hold down).  Then with neg terminal attached push battery all the way back - it catches under a lip of a back hold down.  Then attach front holddown, then pos terminal assembly.  Pop cover back in and replace 3 torx screws and 1 10mm nut.

 

Useful accessory: a voltmeter to put in the front console aux power socket.  I bought this $10 one, with a usb fast charge port:

https://smile.amazon.com/gp/product/B08J7RP74S/

(Pull up 1/4" or so to turn off.)

 

[SnowStorm]

You also need to reset the battery age monitor or the new one won't charge properly (lots of posts by others on this issue).

[ArizonaEnergi]

My 2nd battery in my 2013 Energi has just crashed.  I had the first one put in at the dealer.  Is this a job that is easy, medium or hard to do?  You have posted great instructions and I'm tempted to DIY as it's a hassle going to the dealer these days due to Covid.

Edited April 17, 2021 by ArizonaEnergi

[djc]

Well it is harder than replacing the battery on any other car I have worked on (except that the battery itself weighs less).  There's a full video on replacing the Energi bat, so you can judge for yourself.

 

[ArizonaEnergi]

8 hours ago, djc said:

Well it is harder than replacing the battery on any other car I have worked on (except that the battery itself weighs less).  There's a full video on replacing the Energi bat, so you can judge for yourself.

 

 

Thanks for that video and insight.  I decided to do it and found it not as difficult as I thought it would be but still a pain in the butt.  As I posted elsewhere, I suspect the new battery had a very low charge as it took a lot of time to charge in the car.

 

While it's unlikely I will ever put another one in, I would do it again as it was an annoying task but not that difficult with instructions like yours.

[jzchen]

I can't remember the order I connected the terminals, but if at all possible connect the + terminal first, prior to the -.  It's less likely to spark.